This technical material was developed in June 2014 by the North American SynchroPhasor Initiative (NASPI). NASPI is a collaboration between the North American electric industry (utilities, grid operators, vendors and consultants), the North American Electric Reliability Corporation, academics, and the U.S. Department of Energy, to advance and accelerate the development and use of synchrophasor technology for grid reliability and efficiency. The material attached was produced for one of a series of NASPI technical workshops intended to educate and document the stakeholder community on the state of the art for key synchrophasor technology issues.